Amid growing criticism of Facebook‘s perceived role as a major conduit for hoaxes and half-truths, Mark Zuckerberg once again defended his company’s track record for keeping the social network relatively free of fake news.

“Of all the content on Facebook, more than 99% of what people see is authentic,” he said in a Facebook post late Saturday. “Only a very small amount is fake news and hoaxes. The hoaxes that do exist are not limited to one partisan view, or even to politics.”

In the wake of Donald Trump’s surprise election victory on Tuesday, Facebook has been the target of critics who say the company did not do enough to stop the spread of partisan rumors and hoaxes that fueled Trump’s supporters. Zuckerbergadmitted that fake news is a problem on Facebook, but said the company already works to enable the site’s community to flag such material. He conceded that there’s room for improvement, but indicated that clamping down on fake news is a slippery slope:

This is an area where I believe we must proceed very carefully though. Identifying the “truth” is complicated. While some hoaxes can be completely debunked, a greater amount of content, including from mainstream sources, often gets the basic idea right but some details wrong or omitted. An even greater volume of stories express an opinion that many will disagree with and flag as incorrect even when factual. I am confident we can find ways for our community to tell us what content is most meaningful, but I believe we must be extremely cautious about becoming arbiters of truth ourselves.